Lewis Hamilton was 0.003s faster than team mate Nico Rosberg in practice in Austin today, but it was not a perfect day for the championship leader.

Hamilton was forced to sit out the last part of FP2 after suffering a hydraulic leak, yet another sign of a reliability problems at Mercedes.

“They just said there was some fluid on the floor,” said Hamilton. “There was a leak of some sort, I don’t think it was anything too concerning. It doesn’t help when you lose a little bit of time on the long run, because you get a real good understanding of how much you can push, how much you have to save fuel, and those kinds of things.

“Nico had the whole session and hopefully in terms of the team we’ll learn in terms of the team and understanding the data and everything. For me I guess I’ll get a better feel in the race…”

Meanwhile Mercedes technical chief Paddy Lowe said: “It was a hydraulic issue, quite a small thing. We don’t know exactly what, but we made a precautionary stop. We had two or three things going on at the same time. Reliability is a really important factor in the championship overall, and it’s becoming particularly pointy at the moment with the two drivers heading towards Abu Dhabi, It’s a big challenge for us to make sure we give them sisx car finishes in the next three races.”